I found the
Mandrels quite frightening and they've been a bit of a fave since. I know they are generally regarded as a bit rubbish but i like them.
Another one off monster i like are the
Gel Guards. Again they look a bit rubbish when you see their feet but otherwise i really like the gloopy and totally alien look of them.
The
Wirrn are another race i really like. Again, best not look at how they move though.
The
Fendahleen from
Image of the Fendahl absolutely terrified me as a child. All writhing tentacles and slithery menace.
And agreeing with Mojo. The
Voc Robots,
Axons,
Sea Devils and Pertwee era
Silurians are also classics.
Of the new series, the
Weeping Angels are an excellent creation and need another story where they are the main threat, also the
Silents were a great idea well realised as were the
Sycorax.